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55 comments on Brown Power

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JMG on March 5, 2006 - 5:16pm Permalink | Subthread | Parent | Comments top
dinaz wrote: "Anaerobic digestion does not consume or reduce the nutrient content of manure and organic products. On the contrary, it concentrates it while killing pathogenic organisms present in the manure."

I beg to differ a bit. The die-off of pathogenic organisms depends on the HRT (hyrdraulic retention time) and temperature of digester operation. The most common are plug flow mesophilic systems operating at about 100F and pathogen reduction is only several logs. The thermophilic systems, operating at 140F or higher, essentially produce a sterile product.

With respect to reduction of nutrient content, the most important impact may be the potential reduction of soil carbon, which has an adverse impact on both soil productivity and atmospheric CO2 level. The impact on soil health and productivity is likely a major weak point of all non-food energy production schemes; some refer to these as "dirt burning".

Take a look at:

Building Soils for Better Crops http://www.sare.org/publications/soils.htm (in print and on-line)

The Soil Biology Primer http://soils.usda.gov/sqi/concepts/soil_biology/index.html

Glomalin: Hiding Place for a Third of the World's Stored Soil Carbon
http://www.ars.usda.gov/is/AR/archive/sep02/soil0902.htm

Soil Carbon Center
http://soilcarboncenter.k-state.edu/

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Engineer-Poet on March 5, 2006 - 8:33pm Permalink | Subthread | Parent | Comments top
Which one of those references has test results for soil carbon in those soils fertilized with raw manure vs. liquid digester effluent?  That is what we are debating, after all.
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JMG on March 6, 2006 - 9:23am Permalink | Subthread | Parent | Comments top
None here or elsewhere that I am aware of (with the caveat that I'm not a soil scientist), which is part of my point. Most of the work in this area is looking at the effects on constituents such as NPK. The relationships between soil arbuscular mycorrhizal fungi, glomalin, SOM (Soil Organic Matter), soil microbial diversity and soil management (tillage practices, fertilizer application, crop residues) are very complex and dynamic. This  is a very active research area. Glomalin was only recognized in the late 90's and it appears that there is still considerable controversy on the best techniques to measure SOM. With all the negative connotations of dirt, soil is a very complex but critical environment. Thus we are again perturbing a very complex system, potentially adversely, that we don't yet understand (IMO) sufficiently. Hence the word "may" in my original comment.

Several blogs that cover topics in this area are Muck and Mystery  http://www.garyjones.org/mt/ and Transect Points http://transectpoints.blogspot.com/

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